A radar device with a transmitter and a receiver, as well as with an antenna for transmitting and receiving radar pulses, in which the antenna is arranged at the end of a rotating arm, e.g., of a helicopter rotor or of a turnstile, above the rotor axis, has been known from German Patent No. DE-PS 39,22,086. Such a radar device with synthetic aperture based on rotating antennae is called a ROSAR device. The use of a turnstile instead of the rotor blades does not cause any fundamental changes in the ROSAR principle, and it merely has the disadvantage of a lower lateral resolution, but it also has the essential advantage that the full synthetic aperture length is already reached within short distances. In addition, the turnstile has a high mechanical stability. Such a device can be used near real time in on-line operation, and it can also be used for target reconnoitering and target tracking, besides cartography, obstacle warning or as a landing aid. Another field of application is in the precision approach of missiles. In the prior-art ROSAR device, the result for each distance interval is always obtained by correlation of the received signal with a reference function valid for the distance interval in question.